The demand will rise.
But in economic terms the increase will be trivial compared to the digital market share for still photography as a whole.
1. The market share of new film cameras in 2016 has already been above 20% (mainly due to Instax cameras which alone had 6.5 million units).
2. For a potential / future film camera manufacturer it is completely irrelevant how much digital cameras are sold. The only question is: Can we sell enough film cameras of a certain type profitably.
For example, if Nikon / Cosina / Pentax see the possibility to sell 50,000 35mm SLRs with a profit, they will do it.
No matter whether the market for DSLRs is 2, 4 or 7 million units.
Look at Nikon:
They introduced their completely new designed F6 together with their D2x. Nikon has sold more than 35,000 units so far.
It seems to me, a rise in used film-camera prices would be a negative for Cosina. If there is a significant, long-term increase in used film-camera prices it just makes things worse for companies who can produce new film cameras.
Completely wrong. It is just the other way round: The higher the prices for used film cameras, the more attractive new film cameras will be for potential buyers.
If I have to pay 1,000 bucks for a 20 or 30 year old camera, and 2,000 bucks for a completely new one, lots of people will prefer the new one.
We have already seen that:
In 2008 prices for about 30 year old Plaubel Makinas were in the 1,000 - 1,500 $ range (dependant on condition).
Cosina / Voigtländer saw that and got to the conclusion, that at such prices new cameras of the same type have a market:
Someone who is willing to buy such a 30 year old camera for more than 1,000 bucks, will also be open minded to buy a completely new one for about 2,000 bucks.
That led to the Voigtländer Bessa III / Fuji GF 670.
And the assessment was completely right: AFAIK more than 10,000 units (in total) were sold.
Quite a lot for a "niche in the niche in the niche" like a folding camera.
In total (worldwide) millions of used film cameras are traded each year. The higher the price level, the more attractive new (with guarantee) and improved (there are lots of things which can be improved to former film cameras) film cameras will be.
The increase in Instax usage is a reason to buy a new film camera. People get a photograph (admittedly a low-quality photograph) immediately and it is a tangible thing. But I can buy an Instax camera at WalMart for $37. The best Instax camera you can get (Lomography Lomo Instant Camera) costs $120. How can Cosina make a profit from this trend?
That is very easy: Just make a really good Instax camera (like the former Fuji Fotorama) for Instax Wide. The potential of the Instax film is not exploited at all by the current cheap cameras.
The film is excellent and can deliver much better results with better lenses and cameras.
Cheers, Jan